Currently I have Virgin media - looking at getting FTTP for my next contract. I don't have any existing copper line and I know it will be no problem getting a fibre line installed from the nearest poll (neighbour recently had an install).
My question is - If I take a 12 month FTTP contact on, for example BT.
Aside: I haven't seen BT offer any contracts less than 24 months recently. Aquiss offer 12 month contracts for FTTP, and some other providers do 18.
What would happen if I decided I want to downgrade to a cheaper FTTC deal later on with a different ISP?
It depends. The main question is: does your property have an Openreach copper connection available, or is it a pure FTTP area? The latter is normally only the case for recent new builds.
Several points you should note.
1. BT Retail have three low-cost "fibre" products: "Fibre Essentials" (40M), "Fibre 1" (55M), "Fibre 2" (80M). All three can be delivered either on FTTC or FTTP, at BT's choice.
In areas with only copper, they are all delivered over copper, and in areas with only fibre, they are all delivered over fibre.
In areas with both FTTC and FTTP available, it's complicated. Fibre 1 and Fibre 2 are always FTTP. Fibre Essentials, however, is normally delivered as FTTC, *unless* the speed achieved would be too low, in which case they may use FTTP instead.
(The prices are the same though, regardless of the technology used)
2. Until a few days ago, BT always installed a voice service (there is now the option to order FTTP without voice, at the same price). Sometimes it's done by installing a copper line; sometimes it's done by "digital voice" through the router they supply. There seems to be little rhyme or reason as to which they choose in a particular area. Hence if you order FTTP, they could end up installing copper just for the voice!
3. OFCOM and Openreach are still negotiating over the phased withdrawal of copper. In an area which is being moved from copper to fibre, Openreach would like to do a "stop sell" on copper services, some 1-2 years after FTTP coverage in an exchange area reaches a threshold, maybe 75%. At that point, there's no going back to copper.
Unless you're in Salisbury or Mildenhall, you've probably got a few years before this will affect you.
4. FTTC but I'd use the NTC5 socket that is connected to the ONT?
Not sure what you mean by that. If you mean the FVA (voice) port on the ONT, this is a legacy port and is no longer available for new services. Your BT voice service, if you choose to take it, will be delivered either over a separate copper connection or via Digital Voice on the router.
You can take FTTP from a different provider of course. Sky do voice via their router. With Zen you pay extra for voice, but I don't know how they deliver it. Talktalk don't do voice over FTTP at all.
TBH, I wouldn't worry about the "cheaper" FTTC services if you have FTTP available. For one thing, there might be the cost of installing a copper line if you don't have one already. More importantly, FTTP is *much* more reliable than FTTC. Over time there will be more and more providers available which will continue the downward pressure on prices.